Sulfate resistance of polyvinyl alcohol and basalt fibers reinforced red mud concrete

The present study investigated the reinforcement effects of polyvinyl alcohol fiber (PVAF) and basalt fiber (BF) on the performance of fiber reinforced red mud concrete (FRMC) under sulfate drying-wetting cycle. The underlying mechanisms were further explored through macroscopic performance tests in combination with pore structure, micro-morphology, and phase composition analyses. The results showed that incorporation of BF exhibited a more pronounced improvement in the sulfate resistance of FRMC compared to PVAF. Additionally, FRMC with hybrid PVAF of 0.15% and BF of 0.1% had higher sulfate resistance coefficient (0.854) after 60 cycles, showing the optimal resistance to sulfate attack. The microstructural observations showed that fibers effectively delayed the initiation and propagation of cracks under sulfate drying-wetting cycles. Thus, the fibers provided space for the accumulation of corrosion products, continuously increasing the mass of FRMC, and maintaining overall structural integrity. Pore structure analysis indicated that an appropriate amount of hybrid fibers optimized the pore structure, reducing the porosity and average pore diameter to 20.30% and 26.80 nm, respectively. Meanwhile, the synergistic effect of the fibers delayed the degradation of C-S-H gel, thereby effectively improving the sulfate resistance of FRMC.